AD 98-20-05

This amendment supersedes an existing airworthiness directive (AD), applicable to certain Airbus Model A310 and A300-600 series airplanes, that currently requires, among other things, repetitive inspections to ensure correct synchronization of the hydraulic control valves of the trimmable horizontal stabilizer (THS) actuator; replacement of the horizontal stabilizer actuator motors with new or serviceable motors and resynchronization of the valves, or adjustment of the synchronization, if necessary; and a functional test of the THS. This amendment adds a requirement to replace the hydraulic motor of the THS with an improved motor, which constitutes terminating action for the repetitive inspections. This amendment also expands the applicability to include additional airplanes. This amendment is prompted by issuance of mandatory continuing airworthiness information by a foreign civil airworthiness authority. The actions specified by this AD are intended to prevent desynchronization of the hydraulic control valves, which could result in runaway of the horizontal stabilizer to its full up or down position, subsequent reduced maneuvering capability, and potential pitch upset.

Final rule.

98-20-05 AIRBUS INDUSTRIE: Amendment 39-10771. Docket 97-NM-310-AD. Supersedes AD 96-01-52, Amendment 39-9491.

Applicability: Model A310 and A300-600 series airplanes on which Airbus Modification 11607 has not been installed, certificated in any category.

NOTE 1: This AD applies to each airplane identified in the preceding applicability provision, regardless of whether it has been otherwise modified, altered, or repaired in the area subject to the requirements of this AD. For airplanes that have been modified, altered, or repaired so that the performance of the requirements of this AD is affected, the owner/operator must request approval for an alternative method of compliance in accordance with paragraph (e) of this AD. The request should include an assessment of the effect of the modification, alteration, or repair on the unsafe condition addressed by this AD; and, if the unsafe condition has not been eliminated, the request should include specific proposed actionsto address it.

Compliance: Required as indicated, unless accomplished previously.

To prevent desynchronization of the hydraulic control valves, which could result in runaway of the horizontal stabilizer to its full up or down position, subsequent reduced maneuvering capability, and potential pitch upset, accomplish the following:

RESTATEMENT OF REQUIREMENTS OF AD 96-01-52:
(a) Within 12 days after February 5, 1996 (the effective date of AD 96-01-52, amendment 39-9491), perform an inspection to ensure correct synchronization of the hydraulic control valves of the trimmable horizontal stabilizer (THS) actuator, in accordance with paragraph 4.2.2.1 of Airbus All Operators Telex (AOT) 27-21, Revision 1, dated January 5, 1996.

(1) If the actuator is synchronized correctly, prior to further flight, perform a functional test of the THS in accordance with paragraph 4.2.2.1 of the AOT. Thereafter, repeat the inspection required by paragraph (a) of this AD at intervalsnot to exceed 500 hours time-in- service.

(2) If the actuator is desynchronized slightly, as specified in the AOT, prior to further flight, adjust the synchronization, and perform a functional test of the THS, in accordance with paragraph 4.2.2.2 of the AOT. Thereafter, repeat the inspection required by paragraph (a) of this AD at intervals not to exceed 500 hours time-in-service.

(3) If the actuator is desynchronized significantly, as specified in the AOT, prior to further flight, accomplish either paragraph (a)(3)(i) or (a)(3)(ii) of this AD. Prior to further flight following the accomplishment of either of those paragraphs, adjust the synchronization, and perform a functional test of the THS, in accordance with paragraph 4.2.2.3 of the AOT. Thereafter, repeat the inspection required by paragraph (a) of this AD at intervals not to exceed 500 hours time-in-service.

(i) Remove and replace the hydraulic motors of the horizontal stabilizer actuator (HSA) with new orserviceable motors in accordance with procedures specified in the Airplane Maintenance Manual. Or

(ii) Remove the hydraulic motors of the HSA and perform the various follow-on actions specified in paragraph 4.2.2.4 of the AOT, in accordance with that paragraph. (The follow-on actions include checking the motors and the cam seats, assembling the motors, and metal stamping the modification plate of the motors.) If any discrepancy is found during the check, prior to further flight, repair in accordance with paragraph 4.2.2.4 of the AOT.

(b) For airplanes on which any maintenance action relating to a hydraulic motor or a hydraulic valve block of the HSA has occurred since the airplane was new: Within 12 days after February 5, 1996, accomplish either paragraph (b)(1) or (b)(2) of this AD.

(1) Replace both hydraulic motors of the HSA with new or serviceable motors in accordance with the procedures specified in the Airplane Maintenance Manual. Adjust the synchronization, and perform a functional test of the THS in accordance with paragraph 4.2.2.3 of Airbus AOT 27-21, Revision 1, dated January 5, 1996. Thereafter, perform the repetitive inspections required by paragraph (a) of this AD at intervals not to exceed 500 hours time-in-service. Or

(2) Remove the hydraulic motors of the HSA and perform the various follow-on actions specified in paragraph 4.2.2.4 of the AOT, in accordance with that paragraph of the AOT. Adjust the synchronization, and perform a functional test of the THS in accordance with paragraph 4.2.2.3 of the AOT. (The follow-on actions include checking the motors and the cam seats, assembling the motors, and metal stamping the modification plate of the motors.) If any discrepancy is found during the check, prior to further flight, repair in accordance with paragraph 4.2.2.4 of the AOT. Thereafter, perform the repetitive inspections required by paragraph (a) of this AD at intervals not to exceed 500 hours time-in-service.NEW REQUIREMENTS OF THIS AD:
(c) Within 18 months after the effective date of this AD, replace the hydraulic motors of the THS actuator with improved motors, in accordance with Airbus Service Bulletin A310-27-2081 (for Model A310 series airplanes) or A300-27-6035 (for Model A300-600 series airplanes), both dated November 26, 1996, as applicable. Accomplishment of this action constitutes terminating action for the repetitive inspection requirements of this AD.

(d) As of the effective date of this AD, no person shall install on any airplane a THS actuator having part number 47142-201/-203.

(e) (1) An alternative method of compliance or adjustment of the compliance time that provides an acceptable level of safety may be used if approved by the Manager, International Branch, ANM-116, FAA, Transport Airplane Directorate. Operators shall submit their requests through an appropriate FAA Principal Maintenance Inspector, who may add comments and then send it to the Manager, International Branch, ANM-116.

(e) (2) Alternative methods of compliance, approved previously in accordance with AD 96-01-52, amendment 39-9491, are approved as alternative methods of compliance with paragraphs (a) and (b) of this AD.

NOTE 2 Information concerning the existence of approved alternative methods of compliance with this AD, if any, may be obtained from the International Branch, ANM-116.

(f) Special flight permits may be issued in accordance with sections 21.197 and 21.199 of the Federal Aviation Regulations (14 CFR 21.197 and 21.199) to operate the airplane to a location where the requirements of this AD can be accomplished.

(g) Except as provided by paragraphs (a)(3)(i) and (b)(1) of this AD, the actions shall be done in accordance with Airbus All Operators Telex (AOT) 27-21, Revision 1, dated January 5, 1996; Airbus Service Bulletin A310-27-2081, dated November 26, 1996; or Airbus Service Bulletin A300-27-6035, dated November 26, 1996; as applicable.(1) The incorporation by reference of Airbus Service Bulletin A310-27-2081, dated November 26, 1996, and Airbus Service Bulletin A300-27-6035, dated November 26, 1996, is approved by the Director of the Federal Register in accordance with 5 U.S.C. 552(a) and 1 CFR part 51.

(2) The incorporation by reference of Airbus All Operators Telex (AOT) 27-21, Revision 1, dated January 5, 1996, was approved previously by the Director of the Federal Register as of February 5, 1996 (61 FR 2697, January 29, 1996).

(3) Copies may be obtained from Airbus Industrie, 1 Rond Point Maurice Bellonte, 31707 Blagnac Cedex, France. Copies may be inspected at the FAA, Transport Airplane Directorate, 1601 Lind Avenue, SW., Renton, Washington; or at the Office of the Federal Register, 800 North Capitol Street, NW., suite 700, Washington, DC.

NOTE 3: The subject of this AD is addressed in French airworthiness directive 97-081-217(B), dated March 12, 1997.

(h) This amendment becomes effective on October 26, 1998.

A proposal to amend part 39 of the Federal Aviation Regulations (14 CFR part 39) by superseding AD 96-01-52, amendment 39-9491 (61 FR 2697, January 29, 1996), which is applicable to certain Airbus Model A310 and A300-600 series airplanes, was published in the Federal Register on April 30, 1998 (63 FR 23690). The action proposed to continue to require, among other things, repetitive inspections to ensure correct synchronization of the hydraulic control valves of the trimmable horizontal stabilizer (THS) actuator; replacement of the horizontal stabilizer actuator motors with new or serviceable motors and resynchronization of the valves, or adjustment of the synchronization, if necessary; and a functional test of the THS. The action also proposed to add a requirement to replace the hydraulic motor of the THS with an improved motor, which would constitute terminating action for the repetitive inspections.

Interested persons have been afforded an opportunity to participate in the making of this amendment. Due consideration has been given to the comments received.

The Air Transport Association (ATA) of America, on behalf of one of its members, requests that the proposed compliance time for the replacement of the hydraulic motor of the trimmable horizontal stabilizer actuator be extended from 1 year to 18 months. The commenter bases its request on the limitations of the overhaul vendor, the equivalent level of safety provided by the frequent inspections, and the lack of findings during those inspections.

The commenter has established an aggressive motor replacement program, but has been limited by the ability of the overhaul vendor to modify and return the units. Due to the limited number of spares available and a turnaround time of 20 days, the commenter is only able to accomplish the replacement on one or two airplanes per month. At that rate of accomplishment, this commenter believes 18 months to be the minimum amount of time in which it can accomplish the replacement on its entire fleet.

The commenter also states that, for the past two years, it has been performing the inspection required by AD 96-01-52 at intervals of 500 hours time-in-service on unmodified units, and has yet to find any desynchronized motors. Further, the commenter notes that, since the issuance of AD 96-01-52, the Direction G n rale de l Aviation Civile, (DGAC), which is the airworthiness authority for France, revised the inspection interval to 1,200 flight hours; however, AD 96-01-52 was not revised to reflect this relaxation of the inspection interval.

The FAA concurs with the commenter s request. The FAA has confirmed that the DGAC is in the process of revising its related airworthiness directive to extend the compliance time for accomplishment of the replacement. In light of this, and in consideration of the fact that a more stringent inspection interval of 500 hours time-in-service is retained in this AD, the FAA finds that the compliance time for motor replacement can be extended to 18 months without compromising the safety of the affected fleet. The final rule has been revised accordingly.

Conclusion
After careful review of the available data, including the comments noted above, the FAA has determined that air safety and the public interest require the adoption of the rule with the change previously described. The FAA has determined that this change will neither increase the economic burden on any operator nor increase the scope of the AD.

Cost Impact
There are approximately 88 airplanes of U.S. registry that will be affected by this AD.

The actions that are currently required by AD 96-01-52, and retained in this AD, take approximately 1 work hour per airplane to accomplish, at an average labor rate of $60 per work hour. Based on these figures, the cost impact of the requirements of the existing AD on U.S. operators is estimated to be $5,280, or $60 per airplane.

The new actions that are required by this new AD will take approximately 4 work hours per airplane to accomplish, at an average labor rate of $60 per work hour. Required parts will be provided by the manufacturer at no cost to operators. Based on these figures, the cost impact of the new requirements of this AD on U.S. operators is estimated to be $21,120, or $240 per airplane.

The cost impact figures discussed above are based on assumptions that no operator has yet accomplished any of the requirements of this AD action, and that no operator would accomplish those actions in the future if this AD were not adopted.

Regulatory Impact
The regulations adopted herein will not have substantial direct effects on the States, on the relationship between the national government and the States, or on the distribution of power and responsibilities among the various levels of government. Therefore, in accordance with Executive Order 12612, it is determined that this final rule does not have sufficient federalism implications to warrant the preparation of a Federalism Assessment.

For the reasons discussed above, I certify that this action (1) is not a significant regulatory action under Executive Order 12866; (2) is not a significant rule under DOT Regulatory Policies and Procedures (44 FR 11034, February 26, 1979); and (3) will not have a significant economic impact, positive or negative, on a substantial number of small entities under the criteria of the Regulatory Flexibility Act. A final evaluation has been prepared for this action and it is contained in the Rules Docket. A copy of it may be obtained from the Rules Docket at the location provided under the caption ADDRESSES.

List of Subjects in 14 CFR Part 39
Air transportation, Aircraft, Aviation safety, Incorporation by reference, Safety.

Adoption of the Amendment
Accordingly, pursuant to the authority delegated to me by the Administrator, the Federal Aviation Administration amends part 39 of the Federal Aviation Regulations (14 CFR part 39) as follows:
PART 39 - AIRWORTHINESS DIRECTIVES
1. The authority citation for part 39 continues to read as follows:
Authority: 49 U.S.C. 106(g), 40113, 44701.
39.13 [Amended]
2. Section 39.13 is amended by removing amendment 39-9491 (61 FR 2697, January 29, 1996), and by adding a new airworthiness directive (AD), amendment 39-10771, to read as follows: